Background: Previous reports have shown a significant relationship between suicide ideation and mixed depression. The aim of this study was to explore the prevalence and clinical characteristics of mixed depression among non-violent suicide attempters.

Methods: Using a structured interview (modified Mini International Neuropsychiatric Interview) and assessing all the symptoms of 16 psychiatric diagnoses, the authors examined 100 consecutive nonviolent suicide attempters (aged 18-65) within 24 h after their attempts. Mixed depression was defined as a major depressive episode (MDE)/dysthymic disorder plus 3 or more co-occurring hypomanic symptoms, according to the definition validated by Akiskal and Benazzi [Akiskal, H.S., Benazzi, F., 2003a. Delineating depressive mixed states: Their therapeutic significance. Clin. Approaches Bipolar Disord. 2, 41-47, Akiskal, H.S., Benazzi, F., 2003b. Family history validation of the bipolar nature of depressive mixed states. J. Affect. Disord. 73, 113-122.].

Results: Current mixed depression was present in 63.0% in the total sample, and in 70.8% among the 89 depressive suicide attempters. Irritability, distractibility and psychomotor agitation were present in more than 90% of the subjects with mixed depression. The rate of mixed depression was significantly higher among bipolar than non-bipolar depressive suicide attempters (90% vs. 62%). Patients with mixed depression had the following concurrent disorders: bipolar disorders 41.0%, panic disorder 30.0%, generalized anxiety disorder 89.0%, alcohol abuse/dependence 56.0%, and substance abuse 27.0%. Mixed depression versus non-mixed depression had the following significant associations (odds ratio=OR): females 2.4, bipolar II disorder 9.3, generalized anxiety disorder 41.3, irritability 101.6 and psychomotor agitation 61.1.

Limitations: The study didn't include suicide attempters with very high risk of fatality.

Conclusions: The important new finding of this study is the very high prevalence of mixed depression among depressed suicide attempters. The rates of mixed depression among bipolar and non-bipolar depressive suicide attempters were much higher than previously reported among nonsuicidal bipolar II and unipolar depressive outpatients, suggesting that suicide attempters come mainly from mixed depressives with predominantly bipolar II base. Irritability and psychomotor agitation were the strongest predictors of suicide attempt. From a public health standpoint, our data highlight the necessity of detecting and treating mixed (bipolar) depression in the prevention of suicidal behaviour.